bang path

bang path /n./ An old-style UUCP electronic-mail address
specifying hops to get from some assumed-reachable location to the
addressee, so called because each hop is signified by a
bang sign. Thus, for example, the path
...!bigsite!foovax!barbox!me directs people to route their mail
to machine bigsite (presumably a well-known location accessible
to everybody) and from there through the machine foovax to the
account of user me on barbox.

In the bad old days of not so long ago, before autorouting mailers
became commonplace, people often published compound bang addresses
using the { } convention (see glob) to give paths from
*several* big machines, in the hopes that one's correspondent
might be able to get mail to one of them reliably (example:
...!{seismo, ut-sally, ihnp4}!rice!beta!gamma!me). Bang paths
of 8 to 10 hops were not uncommon in 1981. Late-night dial-up
UUCP links would cause week-long transmission times. Bang paths
were often selected by both transmission time and reliability, as
messages would often get lost. See Internet address,
network, the, and sitename.